MacRumors reports that around half of Apple's 249 U.S. retail services are out of both configurations of the big machines. In some cases there are delays—if you order one of these computers now, you won't be able to get it until at least September 7. This could signal that an expected refresh with Ivy Bridge is coming to the iMacs. An update is long overdue—it was anticipated to come along with the MacBook reboot at WWDC in June, but that didn't happen. And the standard configuration still has Intel's i5 Sandy Bridge chip. While there's an iPhone event in just a few weeks, we wouldn't expect a spec bump to eat up valuable presentation time. So expect this to be an update that shows up without fanfare. [MacRumors via Cult of Mac]